Monisha Perkash of Los Altos Hills follows instructions from Palo Alto Unified School District Nurse Linda Lenoir on how to take a cheek swab to enter into a bone-marrow donor registry. Lenoir held one of many drives Tuesday on behalf of Stanford professor Nalini Ambady, who needs a bone-marrow transplant. Perkash, who has children attending Nixon School in Palo Alto, said she heard about the drive through the Nixon parent communications network. Photo by Chris Kenrick/Palo Alto Online.